Re: Obscure error/warning/information message from git pull

[Teemu Likonen]

Alan Mackenzie [2014-11-18 22:43:26 +00:00] wrote:

>> Well, given the following history (time goes from left to right):
>
>>              - C - D <- foo
>>            / 
>> ... - A - B
>>            \
>>              - E - F <- bar
>
>
>> what branch commit A was made on, 'foo' or 'bar'?
>
> Quite clearly, A was committed on branch foo, since bar didn't exist
> at that time.

No. "A" could have been committed on a private branch called
"asdfasdfasdf" by some unknown person. Then it may have been forget
various ways into that project's commit DAG. Branches are not places.
They just labels (sometimes temporary) that point to a commit. Nothing
more.

Commit operation in Git is like PUSH:

    (defvar a (cons 'original nil))
    (defvar foo a)
    (defvar bar a)

    (push 'commit1 foo)
    (push 'commit2 foo)
    (push 'commit1 bar)
    (push 'commit2 bar)

Both "foo" and "bar" point to a single cons cell. They know nothing
about _variable_ "a" (i.e., branch label). The same applies for Git
branches.

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